This invention relates to air conditioning systems for motor vehicles. More particularly this invention relates to a lubricant distribution system that returns lubricant to one compressor after operating an auxiliary compressor in an air conditioning system.
Many motor vehicles, particularly van conversions and other recreational vehicles (Rvs) have air conditioning systems with dual compressors. One of the compressors in these dual compressor air conditioning systems is a primary compressor driven by the vehicle engine. The other compressor, an auxiliary compressor, is driven by an electric motor rather than through the vehicle engine. The electric motor for the auxiliary compressor may be powered by a generator or by a stationary hook-up such as at an RV park, for example. These dual compressors share a condenser and are connected to alternatively direct refrigerant through one or more evaporators. In these types of systems, both compressors are never operated at the same time. Rather, the primary compressor driven by the vehicle engine is operated when the vehicle engine is running, and the auxiliary compressor is driven when the vehicle engine is not running, such as at an overnight campsite.
Both the engine-driven primary compressor and the auxiliary compressor require lubricating oil for proper operation. However, the lubricating oil in each compressor mixes with the refrigerant being compressed and continuously exits the compressor through the refrigerant lines as the compressor is operating.
The vehicle driven compressors commonly do not have a substantial reservoir of lubricant. These common vehicle compressors with no appreciable sump or lubricant reservoir rely on oil mixed with refrigerant in the compression process to return through the refrigerant conduits to the compressor and shall be referred to herein as entrained lubricant-type compressors. However, in air conditioning systems with an auxiliary electrically driven compressor, the refrigerant does not flow through the primary compressor when the auxiliary compressor is operating. Instead, lubricating oil removed from the engine-driven primary compressor collects in the auxiliary compressor when the auxiliary compressor is operating. Eventually the primary compressor loses adequate lubrication and is damaged by operating in this lubricant starved state.